OFDMA and single carrier FDMA have been selected as the downlink and uplink multiple access schemes for the E-UTRA (Evolved Universal Terrestrial Radio Access) air interface currently being studied in 3GPP (which is a standard based collaboration looking at the future evolution of third generation mobile telecommunication systems). Under the E-UTRA system, a base station which communicates with a number of user devices allocates the total amount of time/frequency resource (depending on bandwidth) among as many simultaneous users as possible, in order to enable efficient and fast link adaptation and to attain maximum multi-user diversity gain.
The E-UTRA system provides for both real time (RT) services, such as VoIP (Voice over Internet Protocol), and non-real time (NRT) services, such as web browsing. The time/frequency resources that allow user devices to use these services may be allocated dynamically (ie on demand at the time that they are needed) or persistently depending on the service used. For example, for real time services such as VoIP, where the amount of resources needed is known in advance, the user devices can be allocated the resources in advance (persistently allocated), for example at the time of the call setup. For more “bursty” traffic, such as web browsing traffic, the resources would be allocated dynamically based on the amount of data to be transmitted between the user device and the network at the time.
The current working assumption in RAN1 is that if the user device has persistently allocated resources in a given Transmission Time Interval (TTI); no other resources could be allocated to the user device for data/signalling within the same TTI, except within the Dynamic Broadcasting Channel (DBCH).